dispatcher | 易学教程

My async Task always blocks UI

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问题 In a WPF 4.5 application, I don't understand why the UI is blocked when I used await + a task : private async void Button_Click(object sender, RoutedEventArgs e) { // Task.Delay works great //await Task.Delay(5000); double value = await JobAsync(25.0); MessageBox.Show("finished : " + value.ToString()); } private async Task<double> JobAsync(double value) { for (int i = 0; i < 30000000; i++) value += Math.Log(Math.Sqrt(Math.Pow(value, 0.75))); return value; } The await Task.Delay works great,

启动一个最简单的Java main程序时有多少个线程被创建

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　在java中，启动一个简单的main程序，并不是只是单单创建了一个main线程而已，JVM会自动创建一些辅助用的线程，主要有以下几个：　　Attach Listener：Attach Listener线程是负责接收到外部的命令，而对该命令进行执行的并且吧结果返回给发送者。通常我们会用一些命令去要求jvm给我们一些反馈信息，如：java -version、jmap、jstack等等。如果该线程在jvm启动的时候没有初始化，那么，则会在用户第一次执行jvm命令时，得到启动。　　Signal Dispatcher：前面我们提到第一个Attach Listener线程的职责是接收外部jvm命令，当命令接收成功后，会交给signal dispather线程去进行分发到各个不同的模块处理命令，并且返回处理结果。signal dispather线程也是在第一次接收外部jvm命令时，进行初始化工作。　　Finalizer：这个线程也是在main线程之后创建的，其优先级为10，主要用于在垃圾收集前，调用对象的finalize()方法；　　Reference Handler：VM在创建main线程后就创建Reference Handler线程，其优先级最高，为10，它主要用于处理引用对象本身（软引用、弱引用、虚引用）的垃圾回收问题。以上这部分内容引用自 http://ifeve.com

Understanding the WPF Dispatcher.BeginInvoke

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问题 I was under the impression that the dispatcher will follow the priority of the operations queued it and execute the operations based on the priority or the order in which the operation was added to the queue(if same priority) until I was told that this is no the case in case of the WPF UI dispatcher . I was told that if a operation on the UI thread takes longer duration say a database read the UI dispatcher simple tries to execute next set of operations in the queue. I could not come to terms

Write PowerShell Output (as it happens) to WPF UI Control

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I've been reading blogs about writing to the UI from different runspaces ( http://learn-powershell.net/2012/10/14/powershell-and-wpf-writing-data-to-a-ui-from-a-different-runspace/ ). I'm basically trying to make it so I can click a button in the UI and run a PowerShell script and capture the output of that script as it happens and update the WPF UI control without freezing up the UI. I've tried a basic example of just writing some output directly, but it seems to hang the UI. I'm using runspaces and dispatcher, but I seem to be stuck on something. Any ideas? Thanks. Add-Type –assemblyName

How to return a value with Dispatcher.Invoke?

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Anyone knows how to return a value from Dispatcher . Invoke in wpf ? I want to return the selected index for a ComboBox . Thanks! user216652 There's another way that returns value from Invoke(): object oIsLoaded = container.Dispatcher.Invoke( new Func<bool> ( () => { return container.IsLoaded; }) ); And by the way, chances are that the initial code (which is working with delegate) won't modify oIsLoaded at all; So I'd rather use a Func<> for returning a value from that kind of function. int result = -1; // this is synchronous myCombo.Invoke(() => { result = myCombo.SelectedIndex; }); return

Spring | 手把手教你SSM最优雅的整合方式

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HEY 本节主要内容为：基于Spring从0到1搭建一个web工程，适合初学者，Java初级开发者。欢迎与我交流。 MODULE 新建一个Maven工程。不论你是什么工具，选这个就可以了，然后next，直至finish。 POM.XML 引jar是一个难点，都是一股脑的引入，这是我们开始的第一步，很关键，我们分开说。先看Spring，我们可能需要的jar：  <dependency> <groupId>org.springframework</groupId> <artifactId>spring-core</artifactId> <version>${spring.version}</version> </dependency>  <dependency> <groupId>org.springframework</groupId> <artifactId>spring-beans</artifactId> <version>${spring.version}</version> </dependency>  <dependency> <groupId>org.springframework</groupId> <artifactId>spring-aop

Deadlock when thread uses dispatcher and the main thread is waiting for thread to finish

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Can someone please explain why this creates a deadlock, and how to solve it? txtLog.AppendText("We are starting the thread" + Environment.NewLine); var th = new Thread(() => { Application.Current.Dispatcher.Invoke(new Action(() => // causes deadlock { txtLog.AppendText("We are inside the thread" + Environment.NewLine); // never gets printed // compute some result... })); }); th.Start(); th.Join(); // causes deadlock // ... retrieve the result computed by the thread Explanation : I need my secondary thread to compute a result, and to return it to the main thread. But the secondary thread must

Is there any way to use Dispatcher on a non WPF thread ; new to multi threading

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问题 Why does this not work? What I am trying to do: I need a way to run specific methods in a specific thread that lives on till the end of the program. My other possible options: As I understand a possible way to do it would be to implement a queue. Into which I could push in methods I want to be run in the specific thread. In the specific thread, I would be spinning and sleeping / monitor.pulse to see if there are delegates waiting to be run in the queue. My objective: Is to avoid all the

Multi-threaded WPF Application: Dispatcher Invoke. A more efficient way?

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问题 Using .NET 3.5 Hi Guys, I'm making a WPF application for a project and I was just looking a bit of insight regarding the Dispatcher and multithreading. An example of my program: Application.Current.Dispatcher.Invoke(DispatcherPriority.Background, new Action( () =>_aCollection.Add(new Model(aList[i], aSize[i])))); Application.Current.Dispatcher.Invoke(DispatcherPriority.Background, new Action( () => _Data.Add(new DataPoint<double, double>(Id, aList[i])))); Application.Current.Dispatcher.Invoke

Dubbo自定义负载均衡

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想了解Dubbo自定义负载均衡实现策略，首先要了解SPI机制，参看文章（ https://www.jianshu.com/p/46b42f7f593c ）了解了SPI机制那么我们基于Dubbo的SPI机制对Dubbo的负载均衡策略进行扩展这里简单阐述下，dubbo的SPI是自己进行了扩展和实现的，所以它的功能比java原生的SPI要丰富一、实现目标 1、如果只有一个dubbo服务提供者，那么直接返回唯一的服务提供者 2、如果没有指定的服务提供者IP，那么使用dubbo默认的随机权重负载均衡 3、如果指定的IP没有对应的服务提供者，那么使用dubbo默认的随机权重负载均衡二、实现代码如下 package com.xxx.balance; import java.util.List; import com.alibaba.dubbo.common.URL; import com.alibaba.dubbo.rpc.Invocation; import com.alibaba.dubbo.rpc.Invoker; import com.alibaba.dubbo.rpc.cluster.loadbalance.RandomLoadBalance; /** * Dubbo负载均衡指定服务IP调用实现（实现规则） * 如果只有一个dubbo服务提供者 * 那么直接返回

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